Changes in 70 teachers' confidence, attitudes and science understanding were tested before and after a major in-service programme. Attitudes were assessed using a 49-item Likert-scale test that probed attitudes to practical science teaching and in-service training. Multi-choice and open-ended questions measured understanding of electricity; melting, dissolving and evaporation; forces; and investigations. Data on pupils' attitudes and cognition were also collected. After in-service, teachers' confidence about science teaching had improved significantly. The majority, but not all, had developed satisfactory levels of understanding and more positive attitudes. Four broad types of response were identified: high attainers who improved attitudes and confidence; teachers with limited science knowledge who found the course difficult but made improvements; unaffected professionals who were already working well and for whom the course had little effect; and disaffected teachers who showed low levels of confidence and competence throughout. Pupil cognition and attitudinal differences related to these types were also found.